SOTEY
494
1-01. ti4
NOTES THE STASDARD HE-ITS OF FOKMATIOS OF TIIF, 10s PAIRS CdI+ ASD ZnI+
siderubly in error because of lack of information concerning the values of the activity coefficients. But if the concentrat,ioIiof the cadmium ions in the BY D. K. -%AIIEF.SOA, G . S . L I ~ L C O L \.\AD I 11. ?; PARTUAsolution is made several times greater than that of it Oliigo Dunedzii .\ Ledand the iodide ions the conceiitrations of Cd13- and XeceiLed October 1 , 1959 Cd142- will be ext,reniely small since the values of the association const,aiits of these species which -4ustin, Matheson aiid Parton' have reported Uiider values of the thermodynamic properties of some of have so far beell published are all two ternis in equation these circumstances the last, the complex ioiiq formed in aqueous solutions of lead and cadmium halides. Calorimetric enthalpies 3 may be neglected. The values of AH1 and AH1 of formation Jvere reported for the lead halide com- t'hen can be calculated from at least tivo equations of plex ions of type I'bX+, but not for the correspond- this simplified form. ing cadmium halide complexes. Approximate Experimental enthalpies of formatioii for the latter species were Apparatus.-The dilution experiments wert~ performed calculat(>dfrom the heat of dilution measurements in a calorimeter of about one-liter capacity zimilar to that of Robiiiwii and lTallace.2 described by Young and 1'ogel.j The potassium iodide We present here the result of a calorimetric solution was contained in a thin-Idled glass bulh of about 10 ml. capacity and was mixed with Y90 ml. of siirrouridiny determiiiatioii of the enthalpy of formation of the solution by breaking the bulb n i t h the I h d e of the staincomplex ion CdI+ nhich is in satisfactory agree- less steel stirrer. The temperature change caused b>- the ment nith the calculated value. The result of lieat of reaction ITUS measured by means of tn-o thermistors a sirnilal. mea.urement for the ion ZnI+ is also re- connected in opposite arms of an EL.?. bridgr, and TVW compared both before and after the breaking of thc. bulb v i t h the ported. temperature change produced by a measllred :tmount of The rc-sultb were ohtained by measuring the heat heat generated electrically in a h-ichrome n-ire liwter. effects produced 1)y the hundred-fold dil&oii of a The heating cxrrent of about 0.3 ampere v a s measured l>y potassium iodide solution firstly nith 0.054 m means of a potent,ionieter and a one ohm stunthird rcsktmcc. period of aboiit four minutw wvizs mcamred Cd(CIOI)n mid iecondly with a perchloric acid Thp heating a on(,-tenth second stop-n:itch. A minimum ten?solution of wch colicelitration that the filial mix- with peratiire change of 0.001" could be detectcd Iiy the change i n tures had the same ioiiic strength ( I ) . These tIvo hicli corrcspondrti to a hetit tcm. Thi' cdorimt~tcrn-as dilution procew's may he represented as 01
KI(n2')
0 0.54 --__
i)/
CIL
rd(c10
ostat :tt 25 f 0 . 0 1 O .
1)
--____f
KI(0 01 111') Ionic strength I I Ql cal. ( I ) Ionic strr,ngtli I,.& cal.
hj- nirasurinp t,he heat of tiilution of :i sodium chloridc solution. Tlic results of this test itn' given in Txble I. :iJst(d
(2)
If it is assumed t1i:it the difference htn-eeii and Qz is due eiitirply t o the forination of complex ions, n+iicli i i i wcin.ii-,iii iodide solutions may he of the fclrni C'diT, Cdl2?CdI,--. CdI4'-, then A& = 81- 0 2 = [CdIi-lAHl
+ [CIII,]AII, r [CdI:j-]AH:i + [CdI:'-]AH,
(3)
In this aquation [CdI+], etc., are the numbers of gram moles of t'he various complex ions in the final solution. and AHl, etc.. are the molar enthalpies of formation of the complex ioiis at the particular ionic strength of the solution. The c.oiicentrations of the rornples ioiis call be calculated from the assocGitioii coiist:ints of the complexes mid the cwicentratioiis of cadniium aiid iodide ioiis. It has tieel pointed out 13)- Touiig and Jo11es3that' the reported values of t h e association coiistaiits for coniplcso:: surh as CdI,,- and C & - niay )IC coli11) .J. 31 A I I S ~ I I1:. I . -1.3Intlirsuii nnd I[. S . P a r t o n . "The Stiiictrirc ited by I\-. J. Ilaiiies, Jnlin X i l e y and
( 2 ) .i. 1.. I
llol~iiisoii nncl IV. E. IVallavr, Ciiem. Ileus., 3 0 , 1!)3
!!442),
( 3 ) 1' t'
y
.I
( ' , ~ u l l e s.11in. ,
/ at thc end of the experiment.
Results In Table I are shown, for both I'b?'" arid C136, the average values of the diffusion coefficient? obtained at each temperature. together with the average deviations of the meawrements.
some indication of polymorphism in the liquid.'O The work reported herein is part, of the larger investigation of molten lead chloride systems, but it is reported a t this time because of the possible novelty of the result's. Experimental Procedure The necessary data m x e collected by the "capillary method" (of Anderson and Saddington." Active material contained within :t capillary was allowed t o diffuse for :L measured time into a large volume of inactive mat,erial of identical c!iemical composition. From the fraction of aclivo mat,erial wmaining in the capillary, together with the c:Lpil. lary length and the time of diffusion, a calculat,ion of the diffusion coefficient was made. The coefficients for Pb?lO ailtl Cl38 $1-ere obtained in stxpar:tte experiments employing only the single : d i v e speries in each instance. The inactive lead chloride was prepared from reagentgrade salt without fwt.her purification except for removal of water. Tiiis was accomplished by maintaining the salt under vaciium :it :t temperature of about 400" for sever:tl hours, while periodically flooding the container with hydrogen chloride to minimize hydrolysis of the lead chloride. PbZlowa,s intxoduced into one portion of the PbC12 and CP6 into :t second portion. Expired-radon needles were pulverized and refluxed for several hours r i t h a concentrated solution of PbCI2. TS'hen the eschanxe had reached rquilihrinni, the solut~ionwas filtered, crystallized, refiltered, washed and dried, with a final vacuum drying as already described. C136 w a s int,roduced by a similar exchange between PbClr and wtive HCI. Groups of P y r r s capillaries, d l about 25 mm. in 1t.ngth ant1 relectcd with idcntic:tl inside di:tmeters of about 0.5 mm.,
J'ol. 64
T ~ A LI E or l ' I P "CI< -----D x 10, C l l l ICIIXTS
T,
411)
2
set
C11. -1
0 0 1 1 1
510 520 530 L54!l
5.50 5 TO
98 i 0 !IS i 06 =t 07 5 08 i
01 OB 04 07 04
PLRE
----
C13'
Pb210
OC.
TU
1 51 0 1 58 i 1 10 i 2 06 i 2 0; i '1 13 i
15 22 01 02 02
14
Since diffuqioii ii a kinetic pheiiomei~on, it is wpected that the diffusion coefficient may be r q m qeiited by a rate equation of the form D = d e\p( - A H * l T i l ' )
in which A H * representi an activation energy for diffuqioii. In all previously reported 11 ork the data for molten salts have fit thiq relatioi141ip w r y well. .iccordiiigly, the data of Table I are again ihown in Figs. 1 and 2, in xhich D has been plotted on a logarithmic scale against the reciprocal of the ahsolute temperature. For I'b?'O the mliieq indicate a linear relationship and the heqt ctraight h e , ohtwined by meaiis of least 5cpareq cnlculatioiis, has the equation D
= !)
28 X
cup( -.3.503 ' I l 7 ' )
The value of 3 X 3 cal. for the activatioli eiiergy ha.: standard error of i133 cal. For the y n l u e s appear more w a t t e r d . The heht .traight line through the points ha5 tlic i'orm tt
D = Ab8 X contractioIi would occiir and the entire capillary Irngth would be filled with active salt n-hen immersed. When (IO) V. T. SlaryansLil. Doklady Akad. iVauk, 68, 1077 (1947). 8. Andcrson and K. Saddington, J. Chem. Sor., Soppl. 381 (1949). (11) J.
exp( -6571) I:? J
Here the value of 8576 cnl. for AIf * ha\ a ~i:~iiclartl error of + 325 cal. It can be Seen that, for CI", the values seem to be grouped very nearly along two approximatelv horizontal lines and theie have been indicated by dashed curves.
NOTES
April, 1960
Discussion The results obtained for Pb"O appear to be normal as compared with the behavior of other cations in molten salts. The results obtained for C136, if we accept the least-squares straight line, also appear normal. The activation energies closely approximate those found for NaCl (5a), whose ions have about the same relative radii. On the other hand, the transference numbers calculated from the measured values of D will have values of about 0 5 as contrasted to the widely accepted, measured value of ahout 0.7 for the chloride ioii in molten PbC1,. l 2 Of course, diffusion and conductance need not proceed by similar mechanisms and this is indicated by the fact that the conductance calculated from the Kernst-Einstein equation, utilizing the measured values of D, significantly exceeds reported values. This has been a geiieral e\;perience u-ith molten d t s . " 5 If, as seomb possible from Fig. 2, there is an a h p t change in diffusion coefficient in the neighborhood of 340" then the behavior is different from that of any ion yet reported. Slavyanskii'O has huggested polymorphism in molten I'bC12 and his data indicate an abrupt change in slope in the 1-icinity of 345" \Then a viscosity @ scale is plotted against temperature. further search of the literature shons other evidence to support the idea of an abrupt change 111 some properties of the melt a t about 540". -1 graphical reinterpretation of the viscosity data of 1'ra>adI3 supports Slavyanskii. The qame reference shon--5 lead bromide to be normal. The surface-tension data of Loren2 and KauflerI4 1% hen plotted againqt temperature show an abrupt change a t about 3.13'. Similar data reported by Ilnhl and I1ukel5 fail t o cover this exact region hit othentiw compare Tvith the data of Lorenz a i d Ihuflci. S o comparable data for other lead wit. could be found, hut it has been suggested by many authors that iiirface tenqion should be a linear frinttion of :emperatiire,16and EO it has proven for other molten salts Such evidence. although meager, leads us to accept the qowibility of the divontinuity shown in Fig. 2. This does not necessarily indicate pol)-morphic behavior in molten lead chloride. The possibility of reaction with the glass vessel cannot be overlooked. Pyrex softens in the temperature raiige under discussion and molten PbCl, readily attwks the glass a t t h e x temperatures in the presence of oxygen. However, oxygen was qcrupiilously excliided from the apparatus and, furthermore the data of Prasad13 indicate normal behavior for lead bromide, which ivould also be cxpectecl to i t t a c k the gla-. In addition. the diff ti-ion cocfficieiit of l'l)zlo shon Y no apparent a h orm ali t y. Coiic1uct:iiicc. cl:rt:1'7 ihon some ahnorrnality in ill' CT I 4 0 1 (lQi8)
J ~ n iC
colonton irnd 11 J L a l d n c r , Cliem H e i s , 58,
r.
R Iluhe, THISJ O L R v i L , 6 2 , 1198 (1958). ( E ) J. L. Ilalil a n d (161 J R P a r i n g t o n . ".in i d x a n c e d Treatise In Ph>siral Chemist r y " Vol 11. Longmans, C r t r n and Co., Ken York, K. Y . , 1951, p. 140
497
the region of 540" but no discontinuity. A niechanism can be proposed, however, T\ hich might account for such conflicting behavior. If n e picture lead chloride, in the vicinity of the melting poiiit, as an equilibrium mixture of free ions and fragmentary residues of the crystalline lattice, a lattice in which the divalent lead is held more tightly than the chlorine, then we can assume that an increase in temperature will bring about an increase in the number of free ions, a decrease in the size and number of the lattice residues, and an expansion among the atoms still composing the lattice. X continued expansion of the lattice will eventually alloJy relatively free movement of the chloride ions through the framework of the lead atoms. A t the temperature a t ivhich this movement becomes sterically possible there would be a discontinuous increase in the diffusion coeficient of the chloride ion. Conductance would mainly involve the free ions, and these would be replenished from the lattice residues as discharge a t the electrodes diifted the equilibrium between the ions and the latticebound atoms. A preliminary examination of the dimensions of the lead chloride crystali8 indicates that the density change observed in going from the melting point to the vicinity of 540" would be approximately sufficient to allow passage of the chloride ion through the lattice, particularly if the expansion were mainly in two dimensions. This is not improbable when it is observcd that the interatomic distances are significantly smaller in one dimension. With or without the discontinuity, the data indicate a larger diffusion coefficient for the larger ion. This is counter to the results obtained for molten salts Containing oiily univalent ions, h i t entirely in accord with the results obtained in ioilic crystalq containing divalent ions. Presence of interniediate ions, such as PbCl+, might explain thi hut evidence for the presence of such flicting. Work now in progress in this Iaboratory qhould provide additional data for clarification of the mechanism of diffusion in molten PbCl, and further discussion will be reserved iiiitil these or other data are available. ( l i ) €€. Bloom and E. Hejrnann, Proc. R a g . Soc (London), Al88, 3 9 2 (1947). (18) €1. Braelken, Z . Xrzst , 83, 2 2 2 (1932).
COPPER(1) CORIPLESES OF -&,4',6,ti'TETRA!SfETHYL-2$ '-BIPYRIDISE BY ROBERTH. LI\NELL~ Department
a/
Y DOROTHY D MIY-FREDI
I'eimont, Bi~r711ir,ton,1-ermont ILcezvtd Oilober S O , 1959
Chemzstrv, Cniaersity
OJ
The prcparation of -t,l',(i,Ci'-tctranir.tll?.l-t','L'bipyridincl (t.bipy.) hni heeii dcvrihed prm ioii-ly' and it< forniatioii o f a Cu(1) complm 1)riefIy studied by Smith.2 The present vork r(ipc,rti the formation of Cu(t.bipg.) and Cii(t.bipy.)a complexes as well as the pKa of the t.bipy. R. H Linnell, J. Org. Chem., 22, 1G91 (195i) (2) G. F. Smith, A n a l . Cham. Acta. 16, 401 (1957). (1)
498
Yol. F-l
?;OTBS
0.10 nitti Sac1 in l o c i f,tOtl -olutioii.
1Iv:asiir(mvnt$ w r r ni:idc at pI1 6.8 :tiid 455 nip, anti :at p H 2.6 xiid 3 3 1 m p . -411 absorlxtncies were measiired on iso:miyl alcohol extracts. The results are sliovn in Fig. 2 . Slaniplcs containing Cu in concentreitions from 5.0 X 10-6to 1.00 X 1 0 - ~ n i o l ~ ~ ~ 1 . ~ - r r e t r e s t e d ~ v i t h a threefold excess of t.bipy. ( o w r that for Cu(t.bipj-.)y),XHa to a pH 5.8, one nil. 5% hydrosylaminc. hydrochloride (in 100 nil. total vol.) and the colored complex extracted with isoamyl alcohol. It w t s found t,hat one extraction quantitatively reniovetl the comples. The abeorhancy at 455 mp \vas linear wit,h concentration x i t h :t mo1:ir absorptivity of 8100. These s:inic isoamyl alcohol c,str:ic'ts were stable \Tit11 time :uid nlmorbancies on(' nionth later checked within *Ic:; of the origil i d \%lUPS.
The influence of :t nuniltrr of (winnion ions on tlie C'ii(T i-t .Iiipy. compl(xwa3investigated. Stuntlsrd d i i t i o n s were prepared containing 0.1 ing. of Cu-
(IT) mid 10 ing. of foreign ion (as nit'rate or chloride saks),
on(' inl. li>-drosylaniinc hydrochloride, SI13 to adjust pII to i i . Y , t .liip>-,in threefold excess, NaCl to ionic starengtliof 0.10. ::lid ni:idti to 50nil. and 10% EtOH. Thv soliitionswrr cst m a t t d once Tvith 10 ml. of isoamyl alcohol and the nixorb:tiiw. measured at 455 mu. The nbsJrbanc.ic,s were in all c:tses ivitiiin 2 6 of ~ the value fbr Cu-t .I)ipy. witlioiit t,lic forc,ign ion. 'Tiiv cations investigated xerc Li, Sa, I\, lIg, ("a, Ba, Cr(II?!, Mii(II), Fe(III), Fe(II), S i ( I I ) , -16.Zii, Cd, IIg(II), ]{&I), .U, S11(1\ ), Sn(II), l%(II),As(l-). AsjlII). Co(1I) : i n l l CdIII). It MXS shoa-n that thcx anions c~hloridc.nitrate. suit ate, acotntc- and pcrclilornto do not iiiterfrrca. Those miioiis d i i c h form insolulilc Cii(1) salts iii iso:irnyl ;ilidiol (iotlitlhCCI,, was the rolor of the second saniplr. Our IsOS was entirely soluble in water and no free iodine was indicated b y starch. The three samples were analyzed by thiosulfate titrations and found to be 99.9, 100.0 and 99.9% Id&.
Results Heats of solution of SHJOa(c), S d O a ( c ) , IVeu Soulh I'C'ales lusliiilzn
R e c e n e d S o r e m b e r 11 1959
The data in thiq note iupplemeiit previoudy published results for the conductancc of hydrochloric acid and hydrogen ion i n aqiieous wrrope and mannitol solutions3-5 by providing values in 5 , 10 and 207, glycerol solutions. Experimental A4n:tlytical rcngent quality glycerol W I Y tliliitetl with dotibly-distilled water (specifir ronductnnrp 1-2 X ohm-' cm.-I) to prepare several stock solutions slightly more concentrated than the desired values of 5 , 10 and 2OC' respectivelv. These \$ere each passed through a mix bed ion-ewhange resin.& Then the conccntrxtion of ea solution was o h i n e d by romp:iring thc mcasured dt sity with values from the literaturc.6 Thr literxture data gave specific gravities caleiilated from n cighinps not corrected for air buovanry ( a correction ~vvhic~his unncccssxrv belom- a SOWo glyrerol concentration). For thr piirposcs of the present work the sperifie gr:tvitirs w w convcrtctl t o densities taking 0.99707 g /ml. D P th(, d r n ~ i t vof wrtrr a t 25'. T h e dc,nsit omposi t ion tint a 111iii o ht:iinf,d wrrv fitted, for r : ~ e h of c w l r:ingcIs of eomlmition, hv the ( 1 ) Presented, in part. in a tlirvis suhrnittrrl in lirtrtial fiilfilln~cntof the requirements of tho Vnirersity of New- En~.ianilfor the degree of Iloctor uf I'hilosojihy. (2) Department of C'heiiiistry, University of \\'isconsin, Rlildisoii 0, Wisconsin. ( 3 ) J. RI. Stokes a n d R. H. Stokes, THISJOGESAL, 60, 217 (1050). (4) J. hl. Stokes and R. H. Stokes, d i d . , 62, 497 (1958). tal R . .J. Steel. J. 31. Stokes and R . H. Stokes, i b t d . , 62, 1514 (19551. (0) >I. Sheely, I n d . Eng. Chem., 24, l O G O (1932).
YOTES
April, 1960 method of h i s t q u n r c s to rqiintions P = ad - h , where a and h were constants, rl th(A drrisity in g./ml. and P wts the \\right per writ . of glj two1 defined by wt. of glycerol 100 P = wt,. of glycerol + F t . of water T A stock solution of 0.8 M hydrochloric acid was prepared by dilution of the analytical reagent. An accurate value of its concentration mas obtained from conductance measurements using the data of Owen and Swecton7and Shedlovsky The standirdizcd glycerol stock solutions were suitably diluted with either water or the 0.8 .TI acid to obtain the solutions whirh were used in the conductance measurements. These dilutions and the conductance measurements are most readily desrrihed by considering an actual case, say 10% glycerol: P a r t of a glycerol stock solution was diluted with water to prepare a water-glycerol solution of P = 10. Another portion of the same stock solution was diluted with the 0 8 J/ acid to give a water-glycerol-acid solution also of I' = 10 (it should he noted that for these ternary solutions P is not the weight per cent. of glycerol in the total solution, but only of the n-atrr-glycerol part). This solution was surccssively diliited Tvith the binary solution of the same P value t o enal)le the conductance measurements to cover the range 0.008-0.1 J I acid concentration a t P = 10. This process of preparing binary and ternary solutions having the sbme P values and using the binary to dilute the ternary solution was repeated a t least twice for each of the three concentrations P = 5 , 10, and 20, respectively. 1\11 weighings wilre referred to vacuum. The 5 , 10 and 20y0 n ater-glycerol solutions had densities and viscosities agreeing t o 0.059 or better with the literature values,6 and had specific condiirtances of about 2 X 10-6 ohm-' em.-*. To find the molaritv of the acid in the glycerol-acid-water solutions the diffewnce in dcnsity between the binary and ternary solutions a t the same value of P had to be known and was assumed to bc n linear function of the arid concrntr'ttion expressed :IS rrt. percentage = 3%.of HCl X 100 n-t. of HC1 wt. of glycerol wt. of water For this purpose the increase in density caused by 1% of hydrochloric acid was taken as 0.00403 g./ml. a t 25'. The conductance measurements were made in an oil thrrmostat a t 25 + 0.002' in the u s u d manner3,' and the rcsistnnces extrapolated to infinite frequency. The values of the eqiiivalcnt conductances a t each glycerol concentration were extrapolated to zero acid concentration by the method of Robinson and stoke^.^ Vse of the d parameter for hydrochloric arid in mater10 gave a satisfactory cstrapolation in a11 the glyrerol solutions.
+
+
Results The limiting equivalent conductances of hydrochloric acid ,io and of hydrogen ion A 0 in the three glycerol solutions are given jn Table I. Transference numbers, obtained from the literature,j were used to calculate the limiting ionic conduct'ances. The maximum experimental error in 110 is estimated as 0.08%. The relative fluidity qo,/q is given for each solution; the value of g is that measured h u e , and go is taken as 0.893 cent'ipoise.
Discussion The remarks made by previous au thors4JSl1regarding conductance measurements for hydrochloric acid in sucrose and mannitol solutions a t 25' seem ( 7 ) B. n. O n r n 2nd F. H. S w e t o n . J . Am. Chcm. Soc.. 63, 2811 (1!21l).
( 8 ) T. Shedlovsky, ibid., 54, 1411 11932). ( 9 ) Robinson and Stokps, "Electrolyte Solutions," Butterworth, Sci. Pii'd.. London, ILngland, 1%5, p. 150. ( I O ) Ref. 9. p. 148. (11) I n ref. 1,Table 1, t h e entries obtained b y this author for hydrochloric acid in 207, sucrose should read A' = 287.4, R = 0.674; and in Table I V of reference 5 t h e values for hydrogen ion in 20% sucrose 239.2 and R = 0.884. should read X o =i
50 1
TABLE I IJMITIXG EQUIVALENT CONDT S C E OF -4CIU" A S D HYDRWESI O N u b I N 5, 10 A N D SOLUTIONS A T 2.5' 5%
10%
~~YDROC'111,I)RIC
L'o'L
C;LYCEROI.
20%
388.9 353.3 283.9 R 0.912 0,829 0,666 A0 319,3 290.2 234.0 r 0.913 0,830 0.669 va/v 0.884 0,774 0.57'3 a )io in cm.2 ( I n t . ohm)-' g. rquiv.-'; R = ,io (in glycerol solution)/ho (in wttpr). *'Ao in rm.2 ( I n t . ohm)-' g. equiv.-'; r = A0 (in glyrerol solution)/ko (in water). 120
t'o apply also t o glycerol. As before hydrogen ion is t'he least aff ected of the univalent, ions by the solution viscosity, and its mobility lies closer to the Walden's rule value than to it's value in pure water.j The viscosity of t,he glycerol solutions appears to be somewhat more effective than t,hat of siicrose or mannitol solutions in retarding hydrogen ion. This has been interpreted for other ions5 as due t o the hydrat'ion characteristics of either the glycerol molecules or the ion being considered.
EXCHAKGE OF RADIOCHLORINE B E T K E E K MOLECI'LAR CHLORIKE ASD CARBOS TETRACHLORIDE BYIRVING M. PEARSON A N D CLIFFORD S. GARNER DepaTtment of Chemistry, Cnaierszty of California. Los A n g e l e s 24, Calzjornia Recened October SI, 1959
I n 1937 Rollefson and Libby2 reported no significant exchange ( t 1 l 2> 7 hr.) when solutions of Clz (37-min. C138label) in CCl, were exposed t o ultraviolet light for 30 min. a t room temperature (enough light absorbed to dissociate all Clz molecules present four times). Later Downs3 found no appreciable exchange in a solution of ClZ (310,000yr. C136label) in CC1, kept in the dark for one week a t room temperature (single experiment). Recently Schulte4 reported significant C12-CCl, exchange (C1'6 label) under the influence of Co60 y rays, ultraviolet, sunlight, and even in the dark a t room temperature. His samples were contaminated with relatively large percentages of HC1 and presumably a radioactive orgaiiochloride impurity (probably formed by attack of C1, on hydrocarbon grease in his vacuum system). Because of the limitations of the previous studies on the dark exchange and because we were interested in its effect on another exchange being studied, we have investigated the C12-CC14 exchange in the dark and in sunlight over long time intervals in systems of high relative purity and a t least 100 times more concentrated in Clz than Schulte's exchange solutions. We have shown that radioactive organochloride impurities have an appreciable effect on the apparent exchange. (1) Supported b y U.S. Atoniic Energy Commission under Contract AT(ll-1)-34 Project h-0. 12 (2) G. K Rollefson and W. F. Libby, J . Chem. Phus.. 6, 569 (1937). (3) J. J. Douns, Ph.D. Thesis, rlorlda State Unirersity, 4ug. 1951, p. 3 5 . (4) J. W Schulte. J. A m . Chem. S o c . , 79, 4643 ( 1 9 5 7 ) .
502 TABLE I C!,-ccl~ EXCI.IAXGE IN eel.: ~ O L I ~ T I OAKT 22-55' Exchsnge IllUl
I.
tini(b,
days
(PI?),.I1
Svt c . i i . n i . " in C12
Net C . I ) , I I I . " i n C'rl,: lwforc~d i b t . nit13r dist.
lOl:k,
-11
SCI'.
'
2r
10' 1 i:b
~'set..
1
2 , 8 =!= 0 . 9 0.9 i1.2 0 . 149 3200 i 40 2 . 1 f 1.1 0 ,\Ig(ClOa), d r j ing tube in inactnv CCl, to 10 ml. for clip-comtnig. St:itistic:il roiinting errors R erc Icept blow 2 7 standard dcviation. Tli A Pyres hulh on it high-vacuum system, frozen a i t h liquid N,,pumped on, and traces of HCl removed b\ suirounding risuallr very small radionctivitr from ail\ potassium halt the bulb with :t n-pentane slush-bath at -130" (vapor pres- present n as corrected for bv determining all tiarkground sur s of C1, and HC1 are ca. 0 2 and 20 mm., respectivelj ) rates, usuallv en 24-25 counts prr minut(>[c.p ni '),on aoluand c )niiwting to an evacuated ti ip a t - 196'. The puri- tions identical in composition n ith thaw I~enigmcu~iired fied C'l, \\as Iahelcd iiy high-temper:iture c~qrulihration~mith except for the :thsenI*e of radio(-hlorinc. Coincidence. corlabelccl \gClpic,ripitittc,d from the labeled HC1 and dried and rections were 1w> than 1°C. Countinq r &te>in CC1, ner(> fused 1 1 1 I neim to remove natcr The labeled C ~vLa s repiiii- converted to an "nqueous" b:ws h7- iiw of :i fartor of 1.03 heti hy the above fractionation procedure, then kept frozen empiricallr drtrrmincd. The m c m i t m t l n r t i dvintion in a bulb on the high-cacuum sjstem, except a h e n being from the mean of the total c p m pt'i m c l ~01 C1- in thc f i v ~ transferr ,d, in order t o minimize attack on the high-temper- cwhange solutions n as onlv 0 8 7 . :tturr-giade Halocarbon glens(' in the stopcock and joints. Results and Discussion Carbon Tetrachloride.-- J T Baker ".4n,tl> zed" CCI, W : I ~ purificd hv the method of W d l ice and w111nrd,7cvrrpt that Seither our nieawremeiits iior thwc of earlier in the i m t d stvp t h r b:tturated solution of C1, in CCl, nac irrxliatc.81 v, ith a 10-n:itt ultrav1olct immersion source foi iiivc estah1i.h the exchaiigc ratc Ian-. one ne('&.. Thc Iiirrified CC'I, ( h p 76.8') n:ts stored in a If, in aiialogy with the Br2-CC13RrewhmgeQin the qraduatetl Pvrex h i l l ) attached to thr high-v~icuiimsj stem. gas phase a i d in liquid CC1, wlutioii at ca. 100Other rhemirals \rere reagent grade. 220", the C12-CC14 exchange rate i q assiimed to Exchange Runs -Known amounts of labeled Clz were condensed at -196' into graduated 12-ml. Pyrex tubes (pre- be given by R = I, (Cl,) 1/!(CC14)= t b ' 'la, iimag' bc viously bahed out and cwtciiatcd) and the solid pumped on calculated from m d fracstionatcd at - 130" as described above Purified R = - [8ah/(4a 2h)tI I n (1 - f ) (1) CCla wa,c distillrd onto the C'lJ (in the dark eucept for occaF = (4a 2b)x/4ayo (2) sional hyief extminittion with a flashlight), the mixtures pumprd on a t -196", fiartionntcd at -130", cooled to where R ig the constant rnte of euchange of C1 -196" a n d the tuhes wiled off hv torch nt a constriction nhile opcsn to a high vnruiim The mixtiire- nere thaneci to atonis (active p l u ~inactive) betmen CClb and CI, room tcrnpcrnture. Onr sollition as proc8esst.d nt once as a in gram-atom< I.-' Gee.-' i n a give11 ruii. F i. the "zero-timr" s:rmple T n o othcis neic kept in the dark a t fraction e-whaiige, mid .T and go arc' the net c p.m. room tcniper,ttiirr, for 48 ant3 21 1 d:n 5 , iesliec~ively,and the of the initially iiiactive CCl, at time t and of the rcmaining t a o wcrv c ~ g o s c dfor the C1, a t zero time, respwtiwly. T7a1u3s of li giJwi in (hiring the d : w :rnd to 1:rhorntor.r~ Table I are h i e d on "after-distillatioii" I valileq. 16 hours pcr tl,rv Aftcr the iiidic~atr~cl tinic, thc (ontents of ich tiibe \ins Table I nlco give. the himolecular rntc coiistant frozen M ith liquid S j , thc tube tip broken ott and thc t u h c k b obtained from eqiiatiouq 1 and 2 tor the asinsrrted quirklv into it g s. fl t i h containing 100 nil. of 0 1 f air-frw KI, thr flask qtopptwd and thc contents stirrcd until sumption R = kb((&)(Crl4), since if the exchange the CCI, had t1i:tard The libcrated I? w : i ~titrated mith iq not of nrdcr 3 / 2 it may well he wand order. standard S:izS,O1 to :L starch end-point. Trace amounts of Rows 6 niid 7 nf Tnhle 1 g i w Schiiltr':: reqiilts for HCl ner-. then tieterminid h> titration with standard haw. comparison F':tch nndyzed mixtiire 4 as acidified s1ightl.r n i t h HSO,, The reductinn in actility of thc C'C1, pha.e on and the phases separated for radioassay. distillation may ari2e from an orga1iochloride imDithizonr and SnCI? spot teats* made on thc "zero-time'' mixture p v e negatlve tests for Hg(1) and Hg(I1) (chlorides purity formed by reaction of C12 n ith 1Talncart)ov of 4hi.h might havc formed h y CI, reacting n i t h traces of greaee wed in the qtopcockq of tho high-vacuum Hg vapor in the high-viiriium SJ stem, and which could ronreivablv evchange nith CCI,); n control test showed that syqtem (wch a "grease chloride" dcliberatcly 0 4 wg of Hg(I1) could have been dctccted in the ea. 15-E. produced under more favorable enixlition< in coilexrhangrb solution. trol euperinicntq was qiixntitatir-ely left hehiiid Radioactivity Determinations .--A 10-ml. aliquot of each nheii CC14 TI^. cliitilled off of wlutionq of the
+
+
(1
( 5 ) J . ,J, Downs and It. E. Johnson. .J. Am. Chem. S o c . , 7 7 , 2098 ( 1 95.5). ( 0 , Ref 3 , p. 1 0 .
( 7 ) t.11. Wallace and J. E. Willard, ibid., 73, 5275 (1950). is! F. I'eipl, "Qualitative Analysis by Spot Test," E l s e v i ~ rF'ublishing Co., K.Y., 3rd English ed., 1940, pp. 49-51.
"greaqe chloride"). I-Tonevcr. tlic ma!l per cent. reduction of activity on distillatinn 4 i o c 11 in rou 4 mid 5 of Table I suggest< that t h c w u a s little organochloride impurity present and that the (9) A. A l l i l l e r and J E TI illard, J C i r m Pi /s
17, lrib (1919)
KOTES
April, 1960 greater per cent. reduction in our other runs w a y probably due to accidental contamination of the CCI, phasc with traces of the highly active aqueour phase or some other radiocontainiiiaiit. The high relati1;e purity of the exchange system may be inferred a l ~ ofrom the fact that the equivalents of HC1 found was only 0.4-0.77, of the equivalents of C1, (in mitrast to 7 and 15% in Schulte’s two runs). The HCI can arise from Clz attacking H20 or stopcock grease in the system. Unpublished experiment iwe have made on the HCl*-CC14 exchange under comparable conditions indicate that it mould caontribute less than 1% based on the upper limit.; for oiir specific dark exchange rates. For the lattcr dark exchange we may take k 3X see.-’ and l i b 8 x lo-” liter mole-’ sec.-’ as conservative upper limits a t
